(a) Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More particularly, the present invention relates to a method of forming a metal line in a semiconductor device using an FSG insulation layer.
(b) Description of the Related Art
An undoped silica glass (USG) insulation layer or fluorine doped silica glass (FSG) insulation layer is usually used as an inter-metal dielectric (IMD) layer in order to form a metal line of a semiconductor device, such as a metal oxide semiconductor (MOS) transistor.
Compared to a USG insulation layer, an FSG insulation layer has a merit in that it can obtain a fast operation speed due to its low dielectric constant (low-k).
However, since an FSG insulation layer includes fluorine, which is an active element, undesired reactions between fluorine and other materials may occur. Such a drawback of an FSG layer will be now described with reference to the accompanying drawings.
FIG. 1 to FIG. 4 are cross-sectional views showing a conventional method of forming a metal line in a semiconductor device using an FSG layer.
Referring to FIG. 1, a lower metal layer 120 is formed on an insulation layer 110 on a semiconductor substrate 100. Although not shown in the drawing, the lower metal layer 120 is electrically connected to another conductive layer at its lower part.
In the case of a MOS transistor, the lower metal layer 120 may be connected to a gate electrode layer or an impurity region in the semiconductor substrate 100.
Referring to FIG. 2, a liner oxide layer 130 is formed on the insulation layer 110 and lower metal layer 120. The liner oxide layer 130 is formed to a thickness of about 800 Å using a chemical vapor deposition (CVD) method.
Referring to FIG. 3, an FSG insulation layer 140 is formed on the liner oxide layer 130. The FSG insulation layer is used as an IMD layer. The FSG insulation layer 140 may also be formed by a CVD method. Subsequently, a USG insulation layer 150 is formed on the FSG insulation layer 140.
Referring to FIG. 4, a via hole 160 penetrating the USG insulation layer 150, FSG insulation layer 140, and liner oxide layer 130 is formed to a degree such that a portion of an upper surface of the lower metal layer 120 is exposed.
In addition, a via contact 170 is formed by filling the inside of the via hole 160 with tungsten W.
Subsequently, an upper metal layer 180 is formed on the USG insulation layer 150 so as to electrically connect to the via contact 170.
However, during a conventional method of forming a metal line in a semiconductor device, the liner oxide layer 130 may not be uniformly deposited on both an upper surface of the lower metal layer 120 and lateral sides thereof. That is, the liner oxide layer is deposited in the desired thickness on the upper surface of the lower metal layer 120, but it is deposited in a relatively small thickness on the lateral sides thereof.
Therefore, since the liner oxide layer 130 on the lateral sides of the lower metal layer 120 cannot properly perform a function of a barrier layer, undesired reactions between fluorine in the FSG insulation layer 140 and materials in the lower metal layer 120 may occur. For example, when the lower metal layer 120 is an aluminum layer, AIF gas may be created by the reaction between aluminum and fluorine.
Consequently, such AIF gas may induce defects of a semiconductor device because the via contact 170 is unstably formed in the subsequent process.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form part of the prior art with respect to the present invention.